The daily grind: Striking the right balance between coffee's health perks and risks 

Studies on caffeine’s effect on heart health have gained traction recently. 

Considering that around one in seven deaths worldwide is caused by coronary heart disease, caffeine’s potential cardio-protective benefits are a critical public health issue.

A study published in the Journal of Clinical Endocrinology and Metabolism in September found that regularly consuming coffee in moderation could help prevent chronic conditions like type 2 diabetes, heart disease, and stroke. The paper reported that the most protective effect was around 200-300mg daily—about two to three cups daily.

The researchers compared non-coffee drinkers (less than 100mg daily) with moderate coffee (200 to 300mg).

Using data from the UK Biobank, with a large sample size of more than 360,000 people aged 37-73, the study found that moderate coffee drinkers reduced the likelihood of developing risk factors for diabetes or cardiovascular disease by up to 48.1%.

Previous studies have assessed the potential benefits of coffee, tea, and caffeine, but their role in the prevention of cardiometabolic diseases such as heart attack, stroke or diabetes has not been clearly defined.

The September study’s results suggest an association rather than a causal relationship. Put simply, the study reported lower levels of cardiometabolic disease in people with moderate caffeine consumption while not proving that moderate caffeine consumption caused this lowered risk.

Nevertheless, its findings have important public health implications as people with a single cardiometabolic disease, such as heart disease, type 2 diabetes, stroke, or non-alcoholic fatty liver disease, have twice the mortality risk of those without cardiometabolic diseases, according to the researchers.

Added to that, those with two or more cardiometabolic diseases have up to a seven times higher risk of dying from any cause.

The study’s lead author, associate professor Chaofu Ke, from Soochow University in China, said: “The findings highlight that promoting moderate amounts of coffee or caffeine intake as a dietary habit to healthy people might have far-reaching benefits for the prevention of cardiometabolic multimorbidity.”

But what happens if your coffee habit means consuming more than three cups daily?

A study not yet published in a peer-reviewed journal but recently presented at the American College of Cardiology (ACC) Asia conference in India found that people who chronically consume caffeine at least five days per week may have an increased risk of cardiovascular disease. 

This was true even in study participants who were otherwise in good health. Chronic caffeine consumption was defined as drinking any caffeinated beverage – including tea, coffee, soda and energy drinks – five days a week over a year. 

The amount consumed was about 400mg of caffeine daily – about four cups of coffee, two energy drinks or ten cans of caffeinated soda drinks.

The researchers found that people who consumed at least 400mg of caffeine daily had increased heart rates and blood pressure over time, which was more pronounced for people who consumed 600mg of caffeine daily.

Lead study author Dr Nency Kagathara of Zydus Medical College and Hospital in Dahod, India, said: “Due to its effects on the autonomic nervous system, regular caffeine consumption could put otherwise healthy individuals at risk of hypertension and other cardiovascular events. Increasing awareness of these risks is vital to improve heart health.”

A study published in the Journal of Stroke in September outlined how consumption of too much coffee along with fizzy drinks, fruit juices and drinks may increase the risk of stroke.

The researchers found that drinking more than four cups of coffee daily raised the likelihood of having a stroke by over a third (37%). However, drinking less than four cups of coffee a day was not associated with an increased risk of stroke.

With caffeinated drinks other than coffee, the researchers found that drinking three to four cups of black tea a day — such as breakfast tea or Earl Grey — significantly lowered the risk of stroke by 29%.

According to a 2021 study published in the journal Nutrients, the cardio-protective benefits of moderate caffeine consumption may be due to enhanced sensitivity to insulin. This means the body responds better to insulin, which can help reduce the risk of type 2 diabetes.

The study outlined how caffeine also has anti-inflammatory properties that are important in preventing chronic conditions like heart disease. Additionally, caffeine may boost fat metabolism, helping the body use fat more efficiently as an energy source, which supports overall metabolic health. However, the specifics of how caffeine acts in the different organs and systems and the mechanisms involved are far from clear.

This emerging research is good news for coffee drinkers like me. My first stop in the morning is an espresso – steaming hot, while I catch up with the news. There is strong evidence that moderate consumption of two to three cups of coffee a day is good for heart health, but more than that should be avoided.

Dr Catherine Conlon is a public health doctor and former director of human health and nutrition, safefood.